This invention concerns the use of threaded fasteners, particularly the field of bolts adapted to be installed entirely from one side of a hole. Such fasteners are commonly referred to as blind bolts.
There is a need for threaded fasteners, particularly in structural steel applications, which can be installed from only one side of a hole so they may be used where the other side of the hole is inaccessible for some reason.
One type of fastener, which can be installed from one side of a hole, includes those commonly called blind bolts. These have evolved over many years and may be suitable for limited structural applications. Examples are described in Australian patent specifications AU-A-67133/90, AU-A-20458/92 and AU-A-20279/95. However a major problem with bolts of that type is that the failure load has a high dispersion and hence the use in structural applications is limited. Also these bolts are relatively expensive to manufacture.
An improved type of fastening system is described in International patent specification WO 00/19113. That system comprises passing a bolt portion of a fastener completely through a hole into which it is being assembled, supporting the fastener on the far side of the hole by means of a tool into which the bolt is screwed, passing a folded collar through the hole and unfolding the collar in order to provide, in conjunction with the head on the bolt portion, a fastener head which is large enough to not pull back through the hole.
While the system described in WO 00/19113 works well, it has now been improved to provide additional advantages. The operation of threading and unthreading the bolt from the tool has been sometimes perceived by users as tedious, and the tool has in some cases been damaged by careless use. Furthermore, the left hand thread provided in the previous invention will not restrain the bolt when undoing the nut hence making it difficult to undo the fasteners. Various aspects of the present invention are intended to provide a fastener, fastening tool and fastening system which overcome these difficulties. The invention may also provide a means whereby a larger diameter collar portion may be passed through the hole.